GC: n
CT: What is Tidal Energy?
Tidal energy is a form of hydropower that converts the energy of the tides into electricity or other useful forms of power. The tide is created by the gravitational effect of the sun and the moon on the earth causing cyclical movement of the seas. Tidal energy is therefore an entirely predictable form of renewable energy, which can be harnessed in two forms:
- Tidal Range: Tidal Range is the vertical difference in height between the high tide and the succeeding low tide. Artificial tidal barrages or lagoons may be constructed to capture the tide. Turbines in the barrier or lagoon generate electricity as the tide floods into the reservoir; water thus retained can then be released through turbines, again generating electricity once the tide outside the barrier has receded.
- Tidal Stream: Tidal Stream is the flow of water as the tide ebbs and floods, and manifests itself as tidal current. Tidal Stream devices seek to extract energy from this kinetic movement of water, much as wind turbines extract energy from the movement of air.
The sea currents created by movement of the tides are often magnified where water is forced to flow through narrow channels or around headlands. There are a number of locations around the coastline of the UK where the tidal stream resource is high, and it is in these areas where early technology developments are taking place to explore the prospect of harnessing tidal energy.
Ramsey Sound and St Davids Head, both in Pembrokeshire, are two such locations and where TEL will test and demonstrate its DeltaStream technology.
S: http://www.tidalenergyltd.com/?page_id=1370 (last access: 7 February 2015)
N: 1. tidal (adj): 1807, a hybrid formation from tide (n.) + Latin-derived suffix -al. A tidal wave (1819) properly is high water caused by movements of the tides; erroneous use for “tsunami, great ocean wave caused by an earthquake, etc.” is recorded from 1868.
energy (n): 1590s, “force of expression,” from Middle French énergie (16c.), from Late Latin energia, from Greek energeia “activity, action, operation,” from energos “active, working,” from en “at” + ergon “work, that which is wrought; business; action”.
Used by Aristotle with a sense of “actuality, reality, existence” (opposed to “potential”) but this was misunderstood in Late Latin and afterward as “force of expression,” as the power which calls up realistic mental pictures. Broader meaning of “power” in English is first recorded 1660s. Scientific use is from 1807. Energy crisis first attested 1970.
2. Kinetic and potential energy associated with the tides.
3. Tidal energy can be converted to mechanical and subsequently electrical form in several ways. The most common is to utilize a single natural basin that experiences tidal flow. The mouth of the basin is blocked by a dam that contains sluice gates and hydroelectric turbogenerators. In operation, water enters the basin through open sluice gates. At high tide the gates are closed. When the tide ebbs sufficiently water is released through the hydroturbines to generate electricity.
4. Old-fashioned term and currently popular expression: blue coal (energy from tides and waves), blue gold (tidal power).
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=tidal+energy&searchmode=none (last access: 7 February 2015). 2 & 3. TERMIUM PLUS – http://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=tidal+energy&index=alt&codom2nd_wet=1#resultrecs (last access: 7 February 2015). 4. OG – https://bit.ly/2LrA1Pb (last access: 19 December 2018).
SYN: tidal power
S: GDT – http://www.granddictionnaire.com/ficheOqlf.aspx?Id_Fiche=8882614 (last access: 7 February 2015); TERMIUM PLUS – http://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=tidal+energy&index=alt&codom2nd_wet=1#resultrecs (last access: 7 February 2015).
